fertile period vs fertile phase

fertile period and fertile phase both are nouns.

Word	Noun	Adjective	Verb	Adverb
fertile period	Yes	No	No	No
fertile phase	Yes	No	No	No

As nouns, fertile period and fertile phase are synonyms defined as:

fertile period and fertile phase: the time in the menstrual cycle when fertilization is most likely to be possible (7 days before to 7 days after ovulation)

fertile period (noun)	fertile phase (noun)
the time in the menstrual cycle when fertilization is most likely to be possible (7 days before to 7 days after ovulation)	the time in the menstrual cycle when fertilization is most likely to be possible (7 days before to 7 days after ovulation)